Substation circuits



Dm 25, 192s. 1,696,274 v K. s. JOHNSON SUBSTATION CIRCUITS Filed Nov. A30, 1926 2 Sheets-Sheet 1 CENT/PAL by l/ /lamey Dec. 25, 1928.

K. S. JOHNSON SUBSTATION CIRCUITS Filed Nov. 30, 1926 2 Sheets-Sheet 2 573 yal Patented Dec. 25, 1928.

UNITED STATES A 1,696,214 PATENT OFFICE.

KENNETH s. JOHNSON, or JERSEY CITY, NEW JERSEY, AssIGNoR To RELI. TELEPHONE LABORATORIES, INCORPORATED, OE NEW YORK, N. Y., A CORPORATION OF NEW YORK.

p suRsTATION CIROUITs.

Application flied November 30,. 1926'. Serial No. 151,627/.

This invention relates to subscriber-saubstation apparatus in telephone exchangesystems and more particularly to the use of amplifiers at subscribers substations lfor increasing the volume of both received and transmitted speech currents.

In accordance with the present invention the filament or cathode of 'such an amplier is supplied with current from a low frequency alternating current source located at the centralofiice and condensers and selective cir-` cuits are provided for'restricting the direct current and low frequency alternatingcur-` rent to the proper circuits at the. substation. Accordingto one aspect of the 1nvent1on a magnetic transmitter is employed which reto the anode of the amplifier as to materially' quires no direct current and according to another aspect of the invention la push-pull transmitter is employed supplied with alternating current, so that in either aspect of the f ,invention practically the full potential of the central Ofce battery is supplied to the plate or anode of the amplifier.

The-use of an amplifier at a subscribers substation is desirable in the case of subscribers who experience difficulty in hearing or being heard over the'telephone. They also have a field where long subscribers loops are necessary or where it is desirable to employ high quality low efliciency transmitters. The use of such amplifiershas been suggested previously but it has been necessary to supply them with current either from a local battery or from the central' office battery. In the latter case the current, consumed by the cathode, and the carbon button transmitter if used, has so reduced the potential supplied affect the output of the amplifier. Where the cathode or filament is supplied with current from an alternating current source as proposed in accordance with the present Invention, practically the full potential ofthe cen-A tral oice battery is availablefor the anode or I late of the amplifier.l

' he invention will be more clearly understood by reference to the following description in connection with the attached drawings in Vwhich Fig. 1 shows an arrangement for ampli-.

tying transmitted speech currents;

Fig. 2 shows an arrangement for ampli-` fying received speech currents;

Fig. f3 shows an arrangement for amplifying both transmitted and received speech currents;

Fig. 4 shows an arrangement for amplitying` transmitted speech currents employlng a push-pull transmltter; and

Fig. 5 shows a modification of thearrange-4 ment of Fig. 4. l

The substation equipment is indicated at A and the central ofiice equipment at B. The

central office, are supplied not only with a direct current battery such as 102, but also with an alternating current generator such as 104. In order to prevent mutual interference the anti-resonant network 103 is connected in series with battery 102. This network is antiresonant to the frequency of the alternating current from sourcelOl.v Condenser 106 excludes direct current from the generator 104 and in combination with inductan'ce 105 vents the transmission to the subscribersv ine of harmonics whichmight falsely operateithe subscribers bell or otherwise interfere with speech transmission.

At the substation the ringer 109'is bridged across the line at alltimes. The bridge also includes the usual condenser 111 for exclud- Ing direct current and in addition the antiresonant network 110, which is similar to' network 103 for excluding the low frequency alternatinr current from the ringer 109. The switchhoo: Contact' is, of course, normally open but when the receiver is removed from the switchhook it is closed to render the amx c ircuit extending from the central oice, over conductor 107 through the secondary wind- Y ing of transformer 113, receiver 114, network 116 which fis of the same general design as networks 103 and 110, condenser 115, switchhook contact 112,J conductor 108 back to the susV central ofiice. Direct current and low freguency alternating current are eliminated rom the receiver by condenser 115 and antiresonant network 116 respectively. The transmitter 117 is of the magnetic type and is included in a local circuit with the primary winding of input transformer 118. Alternating current is supplied to the filament or cath- 0de of amplifier 119 in a circuit which may be traced from one side of the alternating current generator 104 conductor 107, through condenser 122 which excludes direct current, primary Winding of transformer 120, contact of switchhook 112 to conductor 108 and back to the alternating current source. The alternating current in this circuit induces an alternatin current in the secondary winding of trans ormer 120 which heats the filament' of the amplifier. The direct current potential is supplied to the plate of amplifier 119 over a circuit extending from direct current source 102, through anti-resonant network 103, upper left winding of the repeating coil 101 to conductor 107, retard coil 123, primary winding of transformer 113. plate of amp ifier 119, filament of amplifier 119,

throu h the upper and lower halves of the secon ary winding of transformer 120 in parallel, resistance 121, contact of switchhook 112, conductor 108 back to battery 102. The retard coil 123 excludes alternating current of all fre uencies from this circuit.

When the su scriber at substation A talks into transmitter 117, speech currents flow in the transmitter and in the primary of transformer 118. These in turn set up currents in the input circuit of the amplifier which may be traced from the secondar of transformer 118, grid and filament o amplifier 119, through the halves of the secondary Winding of transformer 120 in parallel, resistance 121 to the other side of the Winding of transformer 118. The variations in potential of the grid or control electrode react on the output circuit of the amplifier which ma be traced from the plate of the amplifier, through the primary of transformer 113, condenser 124, resistance 121, upper and lower halves of the secondary of transformer 120 to the filament of the amplifier 119 and back to the plate. The variations in this circuit are transmitted to the secondary of transformer 113 and thence over the circuit traced for receiver 114 to the talking conductors 107 and 108 at the central office where they are re eated throu` h re eating coil 101 to the su scriber at t e ot er end of the talking connection. It will be noted that no biasing battery has been supplied for the grid or control electrode of the amplifier.

In the case of Fig. 2 received s eech currents alone are amplified. There ore transmitter 217 is connected in a circuit similar to the circuit for receiver 114 which may be traced from conductor 207, condens r 215.

anti-resonant network 216, primary winding of transformer 218, transmitter 217, contact of switchhook 212 to conductor 208. Received speech currents also flow in this circuit from which direct current and lov` frequency alternating current are excluded by condenser 215 and anti-resonant network 210, respectively. The circuits for supplying lon' frequency alternating current to the filament of amplifier 219, and direct current potential to the plate of amplifier 219 are the same as in Fig.` l, the corresponding portionsl of the-1 circuits being given the same numbers as in Fig. 1 but in the second hundred. 'lhe numbering of the remaining figures is similar. In this case receiver 214 is connected in :i local circuit in series with the secondary winding of output transformer 213 similmto the connection of transmitter 117 of Fir. 1. Incoming s eech currents are therefor.- supplied to the lnput circuit of amplifier 211* and the amplified speech currents are tran-A mitted to receiver 214.

Fig. 3 provides for the amplification of both transmitted and received speech currents. The circuits for supplyin r direct current and alternating current to t 1e late and filament of amplifier 319 respective y are the same as Figs. l and 2. Likewise, the circuits including the grid or control electrode and the plate of the amplifier are the same. Incomlng speech currents are supplied to the input circuit of the amplifier by means of a circuit extending from conductor 307, condenser 315, anti-resonant network 316, upper half of the secondary winding of transformer 313, primary winding of transformer 318. contact of switchhook 312 to conductor 30. A part of this current also flows through the lower half of the secondary winding of transA former 313, through receiver 314 and trans mitter 317. Speech currents generated by transmitter 317 fiow in a circuit which may be traced from the transmitter, through thi primary winding of input transformer 318 to the mid-point of the secondar winding m transformer 313, whence a part ows through the upper half of the winding to conductor 307, and part flows through receiver 314, bark to the transmitter. Amplified speech cur rents fiowing in the prima winding of output transformer 313 flow t irou h the entire secondary winding of trans ormer 313. throu h the receiver and the transmitter tn the ta 'n conductors 307 and 308.

Fig. 4 s ows an arrangement for amplifying transmitted speech currents with the use of a ush-pull carbon button transmitter activaterf) by means of alternating current. It differs from the disclosure of Fig. 1 only in that the alternating current fiows from conductor 408, through condenser 422, and primary winding of transformer 420, through the upper and lower halves of the primary winding of input transformer 418 in paral- :nagaanl mitter 4l? in parallel and thence back Y over the contact of switch-hook 412 to i amplier at said substation in. cooperative reconductor L107 It will be noted that the positive side of the central otlice battery is connected to conductor 407 which alters the appearance of the circuit somewhat. Since the alternating current flows in opposite. directions through the halves of the primary Winding of input transformer 418, the amplifier 419 is not affected by the alternating current.

ll'ig: 5 differs from Fig. 4 in that the alternating current for transmitter 517 is supplied 'thereto by means of an additional secondary Winding 530 on transformer 520 thus permitting the voltage applied to transmitter 517 to be adapted to the needs ot the transmitter irr'espcctire of the central oce voltage.

What claimed is: 1 ln a tele h'one exchange system, a cen tral o lce, su station apparatus associated therewith including means to receive and produce speech currents, a space discharge lation to said speech current receiving and producing means, a source of direct current and a source of alternating current at said central oihlce, a. common means to transmit current trom said alternating current source to said amplifier and to apply a potentialtroni said direct current source `to said amplifier and means to transmit said speech currents from said producing means to said amplilier,

2. ln a. telephone exchange system, a cenf t'ral, oiiice, substation apparatus associated therewith including a receiver and a transmitter, a space discharge amphiier at said substation operativelyassociated with said receiver and transmitter, said spaced discharge ampliiier including an anode, a cathode and an impedance control element, a source of direct current and a. source of alternating current at said central oilice, a common means to transmit current from said alternating current source to said cathode and' to apply a potential from said direct ycurrent source to said anode, means to transmit current from said transmitter to the input circuit of said amplifier, and meansto exclude said alternating current and saidv direct current from said input circuit.

3. ln a telephone exchange system, a central oce. substation apparatus associated` therewith including a space discharge amplilier, a receiver and a transmitter in cooperative relation theretofor two-way operation,

said space discharge amplifier including an anode. a cathode and an impedance control element, said receiver being located in the output circuitof said amplifieigca source of direct current and a source of alternating. f current at sald centralolice, a common means to transmit current from said alternating current source to said cathode and to apply a potential from said direct current source to said anode and means to applyv incoming speech currents to the control element of said amplifier. Y i

4. In a telephone exchange system, a central office, substation apparatus associated by means ci talking conductors with said central oliice and including a receiver and a high quality, low elciency transmitter tor receiving and producing speech currents, a space discharge amplier at said substation including an anode, a cathode and an impedance control electrode, said transmitter being connected in the input circuit ot said ampliier, a source of `direct' current and a source of alternating current at said central oice, means to transmit current trom said alternating current source to said cathode over said talking conductors, means to transmit a potential from said direct current source to said anode over said talking conductors and means to transmit amplified speech currents to said talking conductors.

5. ln a telephone exchange system, acentral othce, subst-ation apparatus associated therewith including a space discharge amplilier, a receiver and 'transmitter tor 'twon'ay operation in cooperative relation to said amplier, said amplilier having an inputcircuit and an output circuit including a cathrent from said input and output circuits.

G. In a telephone exchange system, a central oilice, substation apparatus associated b v means of talking conductorsv with said central oiiice and including a receiver and a push-pull transmitter for producing and receiving speech currents, a space discharge amplifier at said substation including an anode, a cathode and an impedance control electrode, a source of direct current and a source of alternating current at said central olice, means to transmit current from said alternating current source to said catliode and saidtransmitter over said talking conductors, `means to transmit a potential from said direct current source to said anode over said talking conductors, means to apply speech currents tothe input circuit of said amplifier, and means to transmit amplified speech currents to said talking conductors` 7 In a telephone exchange system, a centra-l oflce, substation apparatus yassociated by means yof talking conductors with said central oilice and including a receiver and a push-pull transmitter for receiving and producing speech currents, a space discharge lCO electrode, a source of direct current and a source of alternating current at said centra A office', means comprising said talking conductors to transmit alternating current tn said cathode from said alternating current source through a transformer, an auxiliary winding on said transformer for supplying alternating current to said transmitter, means also comprising said talking conductors to transmit a potential from said direct current source to said anode, means to apply speech currents to the input circuit of said amplifier, and means to transmit amplified speech currents to said talking conductors.

8. In a telephone exchange system a central office, a subscribers line, substation apparatus associated with said line including means to receive and produce speech currents, a source of direct current and a source of alternating current at said central office, an alternating current consuming device at said substation, said line serving to transmit current from said alternating current source to said alternating current consuming device, common means at said substation for simultaneously conditioning said transmitter and receiver and said consuming device for operation by the alternating current transmitted over said line, said line also providing a path between said substation and said central office for transmitting the direct current from said direct current source to said substation and for transmitting speech currents intwo directions.

9. In a. telephone system, a central office, substation apparatus including receiving and transmitting means for two-way operation, a space discharge amplifier associated in operative relation with said transmitting and receiving means, a line connecting said central office and said substation, means for connecting said amplifier to said line for amplifying the signals transmitted between said central office and said substation, a source of alternating current at said central office, and means for conducting said alternating currentto said substation for energizin said amplifier, said means comprising sai line.

10. In a telephone system, a central office, substation apparatus associated therewith comprising receiving and transmitting means, a space discharge am lifier at said substation comprising a .cat ode voperatively associated with said receiving and transmitting means, a source of alternating current at said central office, and common means for conducting alternatino current from said source to said amplifier tfior energizing said cath ode and for conducting amplified speech currents between said central office and said substation.

11. In a telephone exchange system, a central ofce, a subscribers line, substation apparatus associated with said line including means to receive and produce speech currents, a source of direct current and a source of alternating current at said central office, an alternating current consuming device at said substation operatively associated with said line, said line serving to transmit current from said alternating current source to said alternating current consuming device, 'and a switch at said subscribers station for perinitting the energization of said alternating current consuming device only when said transmitter and receiver are conditioned for operation, said line also providing a path between said substation and said central office for transmitting the direct current of said direct current source to said substation and for transmitting speech currents in two directions.

12. In a telephone exchange system, a central office, a subscribers line, substation apparatus associated with said line including means to receive and produce speech currents a source of direct current and a source of alternating current at said central office, an alternating current consuming device at said substation .operatively associated withsaid line, said line serving to transmit current from said source to said alternating current consuming device, said line also providingY a path between said substation and said cen- 4tral office for transmitting direct current from said current source to said substation and for transmitting speech currents in two directions, and a switch operable at said subscribers station for simultaneously permitting said alternating current consuming device to be energized, and placing said transmitter and said receiver in operative relation with said line.

In witness whereof, I hereunto subscribe my name this 29th day of November A. D., 1926.

KENNETH s. JOHNSON. 

